Changes in Distribution and Abundance of the Loggerhead Shrike

Abstract

The Loggerhead Shrike (Lanius ludovicianus) was once widely distributed and common over most of North America, occupying an exclusive breeding range with no other shrikes. Although it occurs in a wide variety of plant associations, this shrike is generally found in landscapes characterized by widely spaced shrubs and low trees interspersed with short grasses, forbs, and bare ground, habitats which include deserts, scrub lands, savannas, and some agricultural settings. The Loggerhead Shrike seems to have been always most abundant in the southern and western portions of its range, with high breeding densities from Florida across the gulf states to Texas and throughout the arid regions of the West. A northeastward expansion in range occurred in the late 1800s in association with deforestation and agriculture. A similar north central expansion occurred in the 1900s with agricultural development of the northern Great Plains and aspen parklands. Contraction and decrease in numbers have been noted in parts of its range since the 1940s, concurrent with the regrowth of forests, loss of pasturelands, and intensive row‐crop agriculture. More recently, Christmas Bird Count data and Breeding Bird Survey data have revealed an overall downward trend across the continent at least since 1966, although numbers are stable or increasing in some locations. Field studies generally implicate alterations in habitat structure and loss of habitat as factors responsible for changes in breeding distribution and overall abundance. Nevertheless, considering its entire distribution in North America and its historical expansions and contractions of range associated with habitat changes, the Loggerhead Shrike does not appear threatened with extinction as a species. We favor a hands‐on approach to management of the critically endangered subspecies, L. l. mearnsi and L. l. migrans, however, and recommend extensive preservation of the natural scrub desert, shrub‐steppe, western oak savanna, and southern savanna vegetation types, which appear to be optimal, core habitats for this species, as well as fostering land‐use practices that favor shrikes in agricultural and suburban landscapes.

The indirect effects of climate variability on the reproductive dynamics and productivity of an avian predator in the arid Southwest

“…Winter precipitation was the primary driver of nest survival, and overall precipitation was also important. Loggerhead shrikes have experienced range-wide population declines across a variety of habitat types (Cade and Woods 1997;Pruitt 2000), and temperature has been shown to be and important factor in driving success in northern bird populations (Chabot et al 2001;Collister and Wilson 2007;Skagen and Yackel Adams 2012), but the relationship between breeding success and precipitation is first described here. As the !…”

Migratory connectivity in the Loggerhead Shrike (Lanius ludovicianus)

“…Identifying patterns of migratory behavior and nonbreeding season population dynamics remains a high priority, and also a challenge, for most migratory bird species of conservation concern (Elser, 2000;Faaborg et al, 2010;Martin et al, 2007;Runge et al, 2014), in particular, as migratory connectivity impacts the interplay of events throughout the annual cycle (Hostetler et al, 2015). For Loggerhead Shrike, the lack of information on the wintering grounds and wintering ecology has been the greatest obstacle to conservation planning (Cade & Woods, 1997;Pruitt, 2000). Herein, we provide a broad-scale perspective on migratory patterns that both demonstrate the utility of a Bayesian approach using intrinsic markers and add to the growing body of literature regarding its implications for ecology, evolution, and conservation.…”

“…North American Breeding Bird Survey (BBS) data (Sauer et al, 2017) indicate significant (3.18% year −1 ) and range-wide population declines in Loggerhead Shrike since the inception of the BBS in the 1960s, and it has been identified by the North American Bird Conservation Initiative as a "Common Bird in Steep Decline" (Berlanga et al, 2010). Habitat loss due to succession and human development likely contributed to the initial declines (Cade andWoods 1997, Pruitt, 2000), but continued population declines are outpacing habitat loss in the breeding season suggesting other limiting factors (Pruitt, 2000). Migratory populations have experienced more persistent and drastic declines than nonmigratory conspecifics (Sauer et al, 2017), highlighting the need to quantify migratory K E Y W O R D S deuterium, differential migration, leap-frog migration, microsatellites, migratory connectivity, stable isotopes connectivity and migration patterns such that limiting factors on stopover sites and on the wintering grounds can be identified and addressed (Pruitt, 2000;Tischendorf, 2015).…”

Breeding Biology of the Loggerhead Shrike Lanius Ludovicianus in Central Mexico

“…The Loggerhead Shrike Lanius ludovicianus, like many other grassland bird species, has shown sustained declines in abundance across its range over the last few decades (Cade & Woods 1997, Berlanga et al 2010, Fink et al 2022). As such, the Loggerhead Shrike is included, along with many other species, as being of conserva?on concern by the tri-na?onal (Canada-USA-Mexico) Partners in Flight bird conserva?on ini-?a?ve (Berlanga et al 2010).…”

“…In Mexico, it is mainly a breeding resident and is the only one of the two North American shrike species to commonly occur in the country (Howell & Webb 1995). Long-term monitoring data from the Breeding Bird Survey and the Christmas Bird Count in North America have shown substan?al declines of Loggerhead Shrike popula-?ons since 1995 (Sauer et al 1995, Cade & Woods 1997, with an es?mated decline of 3.2% per year between 1966 to 2011 (Sauer et al 2017). More recently, eBird Status and Trends 2007-2021(Fink et al 2022 showed that con?nental popula-?ons con?nue in decline (up to 30%) over most of the species' range.…”